AML-S905X-CC Wiring Tool Overlays Description

Matthew_Splett · February 3, 2023, 7:44am

Ok, I’ve updated my project to use the C preprocessor to apply the includes and use the defines in the wiring tool repository, and that isn’t enough to get this to work. I know I’m getting the correct pin, as when I export it via sysfs I can loop over reading the ‘value’ file and see when my attached device sets it low. There is still no ‘edge’ file when exporting the gpio.

Now I have this: tipi_kernel_module/tipi_le_potato.dts at 0302facc0d517cba39a4b796b33b102ef1f98757 · jedimatt42/tipi_kernel_module · GitHub

    tipi-reset-gpio = <&gpio GPIOX_5 (GPIO_ACTIVE_LOW | GPIO_PULL_UP)>;
    interrupt-parent = <&gpio_intc>;
    interrupts = <MESON_GIC_GXL_GPIOX_5 IRQ_TYPE_EDGE_FALLING>;

So, I tried going back to basics (still Le Potato) with the gpiod tools… I ldto reset my device tree overlays to remove what I had done, and rebooted. Then tried

gpioget gpiochip1 84

That’s fine. Then tried with:

gpiomon -l -f gpiochip1 84

and it replies: gpiomon: error waiting for events: No such device

My understanding is that this gpiod tool, gpiomon, is supposed to be using the /dev/gpiochip1 with ioctl calls to setup the interrupt and then poll it in a totally standards based way.

librecomputer · February 4, 2023, 7:03pm

Le Potato does not support gpio_to_irq so userspace tools do not work, only overlays as IRQ interrupt monitoring is limited.

Overlays should work. You can watch interrupts via cat /proc/interrupts.

blue · April 19, 2023, 7:22pm

Hello @librecomputer I am trying to use an MCP23017 chip on the i2c bus with the i2c-ao.dts overlay.

When I scan the i2c-1 but I only see the addresses of 0x30 and 0x50. I am looking for the address of 0x20 for the MCP23017 device. In the original raspbian image there is an overlay that is applied but I do not believe the original overlays are being applied.

Would you be able to help with accessing the MCP23017 via pins 3 and 5 over i2c please. Thank you!

angus · April 19, 2023, 9:31pm

Have you tried scanning i2c-0? I know if you merge rather than enable overlays it will swap the device numbers. It may happen in other circumstances too.

blue · April 19, 2023, 10:42pm

Hey @angus I have scanned i2c-0 as well. No devices show on that bus

librecomputer · April 19, 2023, 10:43pm

If no device show up, then check your wiring and the I2C bus frequency.

blue · April 19, 2023, 11:00pm

Hey @librecomputer I have verified wiring (it is soldered into a pcba) and can detect the chip with a raspberry pi. How would I check the I2C bus frequency on the libre?

blue · April 20, 2023, 6:34pm

Would you be able to help with a device tree overlay for an MCP23017 at address 0x20 that is compatible with the i2c-ao overlay please. I have attempted to copy an existing overlay and apply the overlay but I am getting an error that the overlay does not exist.

Overall I am not certain if an overlay is needed for the MCP23017 to register at address 0x20. Any assistance would be appreciated. Thank you

librecomputer · April 20, 2023, 11:21pm

After writing the overlay, you need to compile it by running make in the root directory before running sudo ./ldto. Do not run sudo ldto as that will use the system version rather than the newly modified version.

Once you tested it, feel free to contribute it back and it will be pushed in the future.

blue · April 21, 2023, 4:49pm

Thank you @librecomputer I got the new overlay to build and applied it successfully.

Does this look correct?

/*
 * Copyright (c) 2017 BayLibre, SAS.
 * Author: Neil Armstrong <narmstrong@baylibre.com>
 *
 * SPDX-License-Identifier: (GPL-2.0+ OR MIT)
 */

/*
 * Overlay aimed to enable MCP23017 on address 0x20 via I2C_AO on Header 7J1 :
 * Pins 3 (SDA), 5 (SCL)
 */

/dts-v1/;
/plugin/;

/ {
        compatible = "libretech,cc", "amlogic,s905x", "amlogic,meson-gxl";

        fragment@0 {
                target = <&i2c_AO>;

                __overlay__ {
                        mcp23017@20 {
                                compatible = "mcp,23017";
                                reg = <0x20>;
                        };
                };
        };

};

Thank you again

blue · April 21, 2023, 11:07pm

Hello all, I am trying to get an MCP23017 working with a LePotato board.

Would someone be able to help with updating a RaspberryPi overlay here: firmware/mcp23017.dtbo at master · raspberrypi/firmware · GitHub

@librecomputer if you would be able to add this as a supported device it would be much appreciated.

Thank you!

librecomputer · April 22, 2023, 12:46am

We do not have the device to test and verify functionality. The overlay looks correct. You can decompile the Raspberry Pi dtbo via the command dtc -I dtb -O dts FILE.dtbo.

blue · April 24, 2023, 5:15pm

Hello @librecomputer thank you.

I have done the decompile and see that the overlay for the Raspberry Pi has quite a bit more code than my custom overlay above. A few questions:

What sections of the Raspberry Pi .dtbo overlay information do I need to add to the Libre overlay I have above?
Do you have an example of a Raspberry Pi .dtbo that has switched the compatibles, targets, buses, GPIOs, and interrupt for the AML-S905X-CC?
Is there a “master .dtbo” file for the Libre which includes additional info that is shown in the Raspberry Pi .dtbo? I don’t understand why the Raspberry Pi overlay has so much extra code for compatibles, GPIOs and so forth and how this affects the current overlays.

blue · April 24, 2023, 5:42pm

@librecomputer here is what I came up with, any feedback would be greatly appreciated. Thank you!

Change Log (from Raspi .dtbo):
-Changed the compatibles to match Libre
-Updated ‘address’ at fragment 0, 1 and 2 from 0xffffffffto ‘&i2c_A0’

/dts-v1/;

/ {
        compatible = "libretech,cc", "amlogic,s905x", "amlogic,meson-gxl";

        fragment@0 {
                target = <&i2c_A0>;

                __overlay__ {
                        status = "okay";
                };
        };

        fragment@1 {
                target = <&i2c_A0>;

                __overlay__ {

                        mcp23017_pins@20 {
                                brcm,pins = <0x04>;
                                brcm,function = <0x00>;
                                phandle = <0x02>;
                        };
                };
        };

        fragment@2 {
                target = <&i2c_A0>;

                __overlay__ {
                        #address-cells = <0x01>;
                        #size-cells = <0x00>;

                        mcp@20 {
                                compatible = "microchip,mcp23017";
                                reg = <0x20>;
                                gpio-controller;
                                #gpio-cells = <0x02>;
                                status = "okay";
                                phandle = <0x01>;
                        };
                };
        };

        fragment@3 {
                target = <0x01>;

                __dormant__ {
                        compatible = "microchip,mcp23008";
                };
        };

        fragment@4 {
                target = <0x01>;

                __overlay__ {
                        #interrupt-cells = <0x02>;
                        interrupt-parent = <&i2c_A0>;
                        interrupts = <0x04 0x02>;
                        interrupt-controller;
                        microchip,irq-mirror;
                        phandle = <0x03>;
                };
        };

        __overrides__ {
                gpiopin = [00 00 00 02 62 72 63 6d 2c 70 69 6e 73 3a 30 00 00 00                                   00 03 69 6e 74 65 72 72 75 70 74 73 3a 30 00];
                addr = <0x01 0x7265673a 0x30000000 0x27265 0x673a3000>;
                mcp23008 = [00 00 00 00 3d 33 00];
                noints = [00 00 00 00 21 31 21 34 00];
        };

        __symbols__ {
                mcp23017_pins = "/fragment@1/__overlay__/mcp23017_pins@20";
                mcp23017 = "/fragment@2/__overlay__/mcp@20";
                mcp23017_irq = "/fragment@4/__overlay__";
        };

        __fixups__ {
                i2c1 = "/fragment@0:target:0\0/fragment@2:target:0";
                gpio = "/fragment@1:target:0\0/fragment@4/__overlay__:interrupt-                                  parent:0";
        };

        __local_fixups__ {

                fragment@3 {
                        target = <0x00>;
                };

                fragment@4 {
                        target = <0x00>;
                };

                __overrides__ {
                        gpiopin = <0x00 0x10>;
                        addr = <0x00 0x0a>;
                };
        };
};

blue · April 24, 2023, 6:18pm

Got an error on running the above:

root@raspberrypi:/home/pi/libretech-wiring-tool# make
CC      libre-computer/aml-s905x-cc/dt/i2c-ao-mcp23017-a.dts
DTC     libre-computer/aml-s905x-cc/dt/i2c-ao-mcp23017-a.pre.dts
libre-computer/aml-s905x-cc/dt/i2c-ao-mcp23017-a.dts:18.20-24.11: ERROR (phandle_references): /fragment@0: Reference to non-existent node or label "i2c_A0"

libre-computer/aml-s905x-cc/dt/i2c-ao-mcp23017-a.dts:26.20-37.11: ERROR (phandle_references): /fragment@1: Reference to non-existent node or label "i2c_A0"

libre-computer/aml-s905x-cc/dt/i2c-ao-mcp23017-a.dts:39.20-55.11: ERROR (phandle_references): /fragment@2: Reference to non-existent node or label "i2c_A0"

libre-computer/aml-s905x-cc/dt/i2c-ao-mcp23017-a.dts:68.29-75.19: ERROR (phandle_references): /fragment@4/__overlay__: Reference to non-existent node or label "i2c_A0"

ERROR: Input tree has errors, aborting (use -f to force output)
make: *** [Makefile:24: libre-computer/aml-s905x-cc/dt/i2c-ao-mcp23017-a.dtbo] Error 2
rm libre-computer/aml-s905x-cc/dt/i2c-ao-mcp23017-a.pre.dts

librecomputer · April 25, 2023, 6:16am

Copying the Raspberry Pi overlay without understanding what you are doing is not going to work. The Raspberry Pi overlays have extensive hacks to work with Raspberry Pi boards and are usually non-standard. Standard overlays are much simpler.

Daniel_Liao · June 9, 2023, 12:54am

Is there a guide on how you could switch compatibles and such?

librecomputer · June 9, 2023, 2:56am

Linux drivers each have supported compatible strings. They are just names. When you change compatibles in the device tree, you are just telling Linux to change the driver used.

Nicholas_Ferrara · August 3, 2023, 10:16pm

Hi, am trying to operate an LCD screen with the following pin layout from the manufacturer: https://www.waveshare.com/wiki/2inch_LCD_Module#Raspberry_Pi_hardware_connection

Could I use pre existing overlays like the one meant for the 3.5 inch display: AML-S905X-CC (Le Potato) 480x320 ILI9486 SPI Touchscreen Display

Or will I need to create a custom overlay to setup the pin layout communication correctly just as I found someone else doing customization: Custom Device Tree Overlay for MCP23017 via i2c-ao - #2 by blue

Sorry if there is lack of necessary context, I am new to working with modules and these pin layout overlays.

librecomputer · August 13, 2023, 1:38am

Anything less than 3 inches is usually powered by an ST controller rather than an ILI controller. There’s overlays for 240x320 in the wiring tool that was uploaded recently.